In biometric authentication based on a one-to-many identification method not using individual identifying information such as a user ID (identification), the inputted biometric data is verified with all the registered biometric data. Authentication in the one-to-many identification method not using the individual identifying information such as this will hereinafter be termed one-to-many authentication. This one-to-many authentication method has a tendency which depends on performance of a server device in terms of processing time and a processing load.
Further, biometric information varies corresponding to biometric changes due to variations in condition of the living body and ageing. There is a case in which even a valid identical person registered in the system might fail to be authenticated due to the variations in biometric information such as this and a dispersion in method of using an authentication device. Under this circumstance, the one-to-many authentication involves verification the inputted biometric information of the identical person with the biometric information of a different person, and therefore a system threshold of the matching is set high. A rise in the system threshold of the matching, however, leads to an increase false rejection rate in identical person as the case may be.